Ephedra has other alkaloids such as nor-ephedrine which greatly improves the appetite suppressing effects.
Its possible, although there is no answer that I know of to this...but the alkaloids quite possible have a synergistic effect with the ephedrine alkaloid for direct fat burning effects. This is just my theory though so dont take it to heart. I do know Ephedra gave me dramatic results where ephedrine just pretty good.
There was a product called Adipokinex back in the day (not current version) which contained 1R,2S norephedrine HCl which gave the best possible appettite suppression over ephedra and ephedrine. Stim effect was lower too so I here.